1. Field of the Invention
The present invention relates to inkjet printing devices. In particular, the present invention relates to a device with multiple printing mechanisms.
2. Discussion of the Background Art
Inkjet printing mechanisms may be used in a variety of different printing devices, such as plotters, facsimile machines and inkjet printers, collectively referred to herein as printers or printer mechanisms. These printers typically use a printhead to shoot drops of ink onto a page or sheet of print media. Some inkjet printers utilize a type of printhead called a cartridge that carries a self contained ink supply back and forth across the media. In the case of a multi-color cartridge, several printheads and reservoirs may be combined into a single unit.
Other inkjet printers, known as xe2x80x9coff-axisxe2x80x9d systems, propel only a small amount of ink in the printhead across the media, and include a main ink supply in a separate reservoir, which is located xe2x80x9coff-axisxe2x80x9d from the path of printhead travel. Typically, a flexible conduit or tubing is used to convey the ink from the reservoir to the printhead. A printhead may also have a cap or capping, or cleaning mechanism such that when the printhead is not printing, the printhead is covered. This may serve to prevent the printhead from drying and to protect the printhead from the environment.
Each printhead includes a series of nozzles through which the ink drops are fired. The particular ink ejection mechanism within the printhead includes piezo-electric or thermal printhead technology. Two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, Hewlett Packard Company. In a thermal ink ejection mechanism, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heating elements, such as resistors, which are energized to heat ink in the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor.
The nozzles are typically arranged in one or more linear arrays. The linear arrays may be located side-by-side on the printhead, parallel to one another, and substantially perpendicular to the scanning direction. As such, the length of the nozzle arrays defines a print swath or band. That is, if all the nozzles of one array are continually fired as the carriage makes one complete traverse through the print zone, a band or swath of ink appears on the sheet. The height of this band is known as the xe2x80x9cswath heightxe2x80x9d of the printhead, the maximum pattern of ink which can be laid down in a single pass.
The printhead is typically mounted in a carriage that is propelled in a direction orthogonal to the media movement. The carriage may have any number of printheads mounted thereon. To print an image, the carriage is scanned back and forth across above the media in an area known as a print zone. The printhead expels drops of ink as it travels back and forth. By selectively energizing the resistors as the printhead travels, the ink is expelled in a pattern on the media to form a desired image (e.g., a picture, chart or text).
Generally, over time, printers have been developed with an increasing ability to produce more colors, with better resolution, on a larger variety of print media. As inkjet printers are being used in more applications, there is an increasing demand for faster throughput, and an increasing demand for longer print lengths.
Accumulation of fibers on printheads has been an ongoing problem in thermal ink jet printers. Fibers may exist in many forms and may be present in the environment. More typically, fibers are generated by the print media, especially media made of paper or textiles. Fibers can adhere to printheads and cause a print quality defect known as xe2x80x9cfiber tracksxe2x80x9d in which the fiber becomes wet with Ink and acts like a paint brush on the print media. The resulting artifact is an undesired streak of ink across the printed media.
The traditional solution to this problem is to design the printhead so that the nozzle plate is closer to the printed media than any other feature on the printhead. While advantageous for print quality, this increases the possibility of a short fiber causing fiber tracking. In addition, the design of the xe2x80x9cservice stationxe2x80x9d includes features to remove fibers from the printheads. In principle, the combination of a well designed printhead, service station, and printhead cleaning algorithms may mitigate, but not eliminate, problems associated with fibers. This solution is adequate in printing environments where time can be taken to service and wipe the printheads frequently during or in between a print job. However, due to the time needed for this action, the ink deposited before the servicing operation may dry, producing a xe2x80x9cbandingxe2x80x9d appearance. Multi-pass print modes may be implemented to reduce the appearance of xe2x80x9cbanding,xe2x80x9d but these may add additional time to a print job. Another solution may be to perform servicing in conjunction with an empty swath. However, for very long print jobs having no empty swaths, there is a high risk of contamination and defects.
Another problem encountered in certain printing applications, for example in the publishing and textile industries, is that additional colors may be required over and above those that can be mixed or synthesized from the traditional high and light dye load primary colors of cyan, magenta and yellow typically found in a color printer. These additional colors are referred to as xe2x80x9cspotxe2x80x9d colors and are usually pre-formulated with specific properties. In the analog printing systems for the publishing and textile industries, customers have a large range of inks, colors, and options for special configurations. There are hexachrome printers available that add greens or oranges to the primary colors.
In addition, there may be a need to treat the printed media after printing, for example, to apply a fixative or other coating to the finished print job.
Thus, it would be desirable to implement a printing system architecture that provides for faster throughput. It would also be desirable to implement a printing system that prevents the accumulation of fibers on the printhead and eliminates fiber tracks. It would further be desirable to implement a printing system that allows a user to configure and customize spot colors, special treatments or coatings for application during printing.
In a production environment where print speed is essential, the current fiber management techniques require an undesirable amount of time. In the realm of digital textile printing where speed and long runs of potentially fibrous fabrics are used, the present invention is of particular interest and has clear advantages over more traditional systems.
A printer is disclosed that includes one or more first print bars each having a first printhead carriage, one or more first printhead service stations for servicing each of the first printhead carriages, one or more second print bars each having a second printhead carriage, and one or more second printhead service stations for servicing each of said second printhead carriages. The printer also includes first circuitry for controlling the one or more first print bars and the one or more second print bars such that while the one or more first printhead carriages are being serviced the one or more second print bars are in operation.
The printer also includes circuitry for recognizing the number of print bars and the number of printhead carriages present in the printer and for formatting print jobs to utilize the recognized number of print bars and printhead carriages.
It should be understood that the printer and the printbars are configured such that any number of print bars, preferably two or more, may be installed in the printer. It should also be understood that during periods when no service is required, the printbars may print simultaneously.
The first printhead carriage may include a number of printheads organized in a certain order along a scan axis, and the second printhead carriage may include a number of printheads organized in an order opposite that of the first printhead to mitigate artifacts associated with bi-directional printing. The number of printheads in the first and second printhead carriages may be used to generate print masks. This is advantageous in that a larger population of nozzles are available for use in generating the masks. In addition, by having multiple printhead carriages, uninterrupted printing can occur without interrupting the main servicing of the other print carriages.
In another embodiment of the invention, a printer is disclosed that includes multiple print bars, each having at least two print bars, and at least one printhead service station for servicing the print bars. Each print bar has a plurality of print heads in a page wide configuration. The printer also includes first circuitry for controlling the one or more of the print bars such that while one or more of the print bars are being serviced, at least one other print bar is in operation. By having multiple print bars in page wide configurations, uninterrupted printing can occur without interrupting the main servicing of the other print bars.
Other features and advantages of the present invention include the ability to replace the printhead while the printhead carriage is being serviced, and to automatically align the replaced printhead, the ability to print spot colors and the ability to apply coatings to the print media.